<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form action="/mail" method="post">
    请输入验证码：<input type="text" name="code" id=""> <br>
    <input type="submit" value="提交">
</form>
</body>
</html>